Aqueous biphasic hydrogenations catalyzed by new biogenerated Pd-polysaccharide species

A palladium species bound to an exopolysaccharide (Pd-EPS) was obtained from alive bacterial cells of Klebsiella oxytoca BAS-10 grown in static mode in the presence of Pd(NO3)2. Pd-EPS, after isolation and purification, was used as catalyst in the aqueous biphasic hydrogenation either of unfunctionalyzed olefins, as styrene, 1-octene and 1,3-diisopropenylbenzene, or of some α,β-unsaturated aldehydes. The catalytic system was very active under mild reaction conditions and its activity was maintained in some recycle experiments. Even more efficient was the “activated Pd-EPS”, obtained by a pre-treatment of Pd-EPS with 1 MPa of H2 at 30 °C for 21 h; while Pd-EPS originally contains only Pd(II), as demonstrated by XPS measurements, the activated catalyst shows the presence of both Pd(II) and Pd(0) in the ratio 1.9/1. The two catalytic systems show different structures at TEM observations evidencing the transformation of electron ultradense nanoaggregates (Pd-EPS) into jagged microaggregates (“activated Pd-EPS”).

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (120 K)Download as PowerPoint slideHighlights► Pd-EPS was prepared by Klebsiella oxytoca fermentation in the presence of Pd(NO3)2. ► Activated Pd-EPS was obtained by hydrogen treatment of Pd-EPS. ► Both palladium catalysts were active only in the presence of water. ► Both catalysts were easily recovered and reused in recycling experiments.